1. Technical Field
The present invention relates to a control method and device for position-based impedance controlled industrial robot, and more particularly, a control method and device for position-based impedance controlled industrial robot able to improve contact stabilization with regard to an environment with a variety of stiffness.
2. Description of the Related Art
Industrial robots have been widely used in process automation in accordance with industrial development.
These industrial robots require not only motion control but also force control for safe interaction between robots and environment (task target) when task is performed while in contact with an external environment.
During the last 30 years, numerous force control methods for a safe contact task for robots have been proposed. These force control methods can be classified mainly into impedance control methods and hybrid position/force control methods.
Hybrid position/force control methods are methods controlling each force and position separately, and having a disadvantage of requiring a switching algorithm.
Impedance control methods are methods with a goal for robots to have desired impedance and thereby interaction between robots and environment is performed, and having an advantage of requiring no switching algorithm.
Since commercial industrial robots generally include precise robust position controllers, a position-based impedance control (PBIC) with the advantage has been proposed.
But, the position-based impedance control cannot guarantee contact stability because environmental parameters may exceed a fixed range and may be altered in a variety of ways. To make up for this, advanced control theories such as adaptive control, robust control, etc. are being applied, but i) system complexities increase, and designing precise adaptive rules and actual implementation is difficult for adaptive control, ii) robust control considers mostly little uncertainties, whereas, environment can possess a variety of properties from soft to very strong, and efficiency in performance and cost decline when large uncertainties are considered.
Conventional energy-bounding algorithm guarantees robust stabilization for interaction with a virtual environment. The conventional energy-bounding algorithm possess two control parameters corresponding to an environmental change, but the performance is limited in that control parameters are considered as constants and possess problems in that no detailed design method for control parameters is provided.